Using dev build 0.53.103608, I see that the MXM is now described as a "MXM 6.5 mm" in caliber 6.5 x 39 mm, and that the tooltip descriptions the "6.5mm 30Rnd STANAG Mag" and the "6.5mm 100Rnd Tracer (Red) Belt Case" magazines both list the MXM as among their compatible weapons. However the weapon is not compatible with the Sound Suppressor (6.5 mm NATO) but rather still compatible only with the Sound Suppressor (7.62 mm) despite now only being only compatible with and loading the 6.5 x 39 mm STANAG caseless magazines used in all of the MX series rifles.

EDIT: The issue persists as of dev build 0.55.103960 and stable build 0.54.103957.

Steps To Reproduce

Using the Editor as of dev build 0.53.103696:
1. Place a BLUFOR Marksman somewhere in Stratis.
2. Add to the Marksman's init: this addPrimaryWeaponItem "muzzle_snds_B"
3. Place a [BLUE] Basic Ammo box in front of the Marksman.
3. Click Preview, then once in the game world "aim" at the ammo box until the action menu option for "Inventory" is available and select that option.
4. Drag a "6.5mm 30Rnd STANAG Mag" from the crate tab into the MXM's magazine slot.
5. After the loading animation concludes, mouse over the 2D pictures of the MXM, the inserted magazine and the suppressor and read their tooltips.

ALTERNATELY
1. Place a unit somewhere in Stratis.
2. Add to the unit's init: removeAllWeapons this; this addMagazine "30Rnd_65x39_caseless_mag"; this addWeapon "arifle_MXM_f"; this addPrimaryWeaponItem "muzzle_snds_B"
3. Click Preview.
4. Press the Inventory key, then mouse over the weapon, its magazine and its muzzle accessory and read their tooltips.

ALTERNATELY
1. Place a Marksman somewhere in Stratis.
2. Add to the Marksman's init: this addPrimaryWeaponItem "muzzle_snds_B"
3. Click Preview.
4. Press the Inventory key, then and mouse over the weapon and its muzzle accessory and read their tooltips.